Water damage is tricky, you need to open the system and clean up the remaining liquid and the corrosion that is left. You may need to replace some of the parts (including logic bds.) But you won't know until you see whats damaged.

It's been clean up already (with denatured alcohol) . That was very few white traces of water. As it works fine with new charged battery, I am wondering why do I need to change mother board ? Diagnostic tends to lead to change the megasafe board instead, but I'd need feedback from some guru of mac ...

1 Answer

Jean, Apple moved the power switching logic to the main logic board on this model so changing the DC in board won't help you here. While it's possible the DC in board also needs replacing its not were I would start given the symptoms you've outlined here. Have you run the Apple's Hardware Test yet to see what it discovers? Here's a link on how to access it AHT